Loans and Investments - Non-Performing Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2024	Dec. 31, 2023
Loans and Investments
UPB	$ 507,659	$ 427,929
Loans and investments, gross	12,249,862	12,615,006
Non-performing loans
Loans and Investments
UPB	464,827	274,152
61 - 90 Days Past Due \| Non-performing loans
Loans and Investments
Loans and investments, gross	0	0
Greater Than 90 Days Past Due \| Non-performing loans
Loans and Investments
Loans and investments, gross	464,827	274,152
Multifamily
Loans and Investments
UPB	352,223	272,493
Multifamily \| Non-performing loans
Loans and Investments
UPB	462,207	271,532
Multifamily \| 61 - 90 Days Past Due \| Non-performing loans
Loans and Investments
Loans and investments, gross	0	0
Multifamily \| Greater Than 90 Days Past Due \| Non-performing loans
Loans and Investments
Loans and investments, gross	462,207	271,532
Commercial
Loans and Investments
UPB	1,700	1,700
Commercial \| Non-performing loans
Loans and Investments
UPB	1,700	1,700
Commercial \| 61 - 90 Days Past Due \| Non-performing loans
Loans and Investments
Loans and investments, gross	0	0
Commercial \| Greater Than 90 Days Past Due \| Non-performing loans
Loans and Investments
Loans and investments, gross	1,700	1,700
Retail
Loans and Investments
UPB	19,521	19,521
Retail \| Non-performing loans
Loans and Investments
UPB	920	920
Retail \| 61 - 90 Days Past Due \| Non-performing loans
Loans and Investments
Loans and investments, gross	0	0
Retail \| Greater Than 90 Days Past Due \| Non-performing loans
Loans and Investments
Loans and investments, gross	$ 920	$ 920

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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